Merge pull request #315 from reactive-streams/gradle-2.12-update

Update to Gradle 2.12

Author: viktorklang

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-2.12-bin.zip